The objective of this study was to examine the relationship between the enzymatic activity of aspartate aminotransferase (AST) in seminal plasma and in spermatozoa to semen quality parameters in boars. Semen volume, sperm motility, sperm concentration, percentage of morphologically abnormal spermatozoa (MAS), total number of spermatozoa per ejaculate and the AST activity in supernatants and in spermatozoa was assessed in 102 collected samples of semen fertile AI boars. AST activity in supernatant correlated negatively with sperm motility (P